<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var num = prompt("请输入一个数：")
        var flag = true;
        function go(num){
            for(var i =2 ;i<num/2;i++){
                if(num%i==0){
                    flag = false;
                }
            }
            if(flag==true&&num!=0&&num!=1){
                alert(num+"是素数")
            }
            else{
                alert(num+"不是素数")
            }
        }
        go(num)
    </script>
</body>
</html>